CN104185241A - Routing method suitable for restricted satellite network - Google Patents

Abstract

The invention discloses a routing method suitable for a restricted satellite network. All satellite nodes using the method provide data relay service for other satellite nodes in a storing, carrying and forwarding mode, and in the severe network environments of failure of the satellite nodes of the preset proportion or the preset number, frequent interruption of links among satellites and the like, data packets can be transmitted among the source/destination satellite nodes in a hop-by-hop mode by utilizing communication opportunities formed by periodical moving of the middle satellite nodes.

Description

Be applicable to the method for routing of tethered satellite network

Technical field

The present invention relates to satellite communication field, the satellite network method for routing under the adverse circumstances such as the particularly satellite node of preset ratio (or predetermined number) inefficacy, the frequent interruption of inter-satellite link.

Background technology

Satellite network is the important component part of national information infrastructure, is bearing the communication task such as emergency disaster relief, Scientific Exploration, has huge application prospect in civil and military field.

Route technology is in occupation of critical role in Satellite Networking, and it has directly determined transmittability, communication efficiency and the service quality of satellite network.In order to solve satellite network routing issue, researcher both domestic and external has successively proposed a series of technical scheme, comprise, explicit multi-path routing algorithms (Compact Explicit Multi-path Routing, CEMR), probability Routing Protocol (Probabilistic Routing Protocol, PRP), assist location On-demand routing algorithm (Location-Assisted On-demand Routing, LAOR), datagram routing algorithm (Datagram Routing Algorithm, DRA), multilayer satellite routing algorithm (Multi-Layered Satellite Routing Algorithm, MLSR), satellite packet Routing Protocol (Satellite Grouping and Routing Protocol, SGRP), layering satellite routing algorithm (Hierarchical Satellite Routing Protocol, HSRP) etc.Although these existing methods can be competent at the route task in general satellite network, because they are based on same network topology hypothesis completely, namely, the dynamic change of (1) satellite network topological structure is predictable; (2) probability of unexpected generation link down, node failure is very low, so that negligible, so in range of application, there is larger limitation, for the satellite node of preset ratio (or predetermined number) lost efficacy, the frequent Satellite Networking problem of the severe net environment such as interrupting of inter-satellite link is helpless.

Summary of the invention

Embodiment of the present invention technical problem to be solved is: how to realize satellite network route technology at the severe net environment such as satellite node inefficacy, the frequent interruption of inter-satellite link of preset ratio (or predetermined number), complete the transmitted in packets from source satellite node to object satellite node.

The technical solution used in the present invention is:

Proposed a kind of method for routing that is applicable to tethered satellite network, its concrete steps are:

1., when source satellite node sends grouping to object satellite node, the first satellite node that receives this grouping is stored this grouping and carries this grouping and move according to the track of self in buffer memory; Setting the first satellite node is the current satellite node that carries grouping;

2. the current satellite node that carries grouping uses tethered satellite forwarded algorithm to select down hop satellite node, and the moment of meeting with down hop satellite node at the current satellite node that carries grouping, the current satellite node that carries grouping by this forwarding of packets to down hop satellite node;

If 3. this down hop satellite node is object satellite node, complete transmitted in packets; Otherwise, this down hop satellite node is set as currently carrying the satellite node of grouping and proceeding to step 2..

Wherein, described step 2. in, use tethered satellite forwarded algorithm to select the concrete steps of down hop satellite node to be:

21 in predetermined period, each outbound link generation state measurement value that the current satellite node that carries grouping is it according to initial topology structure and forwarding statistical information, and then use Link State distribution method that this link-state metric value is diffused into whole tethered satellite network;

22 in the time that needs are selected down hop, and this current satellite node that carries grouping, by the link-state metric value set receiving, splices satellite network topological view, then uses dijkstra's algorithm on this topological view, to calculate down hop satellite node.

Wherein, the initial topology structure in described step 21 is that satellite node obtains from ground station, and this initial topology structure is made up of in the time period of open mode the each outbound of satellite node.

Wherein, in described step 21, the concrete steps that the current satellite node that carries grouping is each outbound link generation state measurement value according to initial topology structure and forwarding statistical information in predetermined period are:

The 2101 current satellite nodes that carry grouping, by predetermined period, on the basis of initial topology structure, in conjunction with the forwarding of packets situation of self record, upgrade the forwarding statistical information of each outbound;

The 2102 current satellite nodes that carry grouping obtain forwarding statistical information input negative exponential function the link-state metric value of each outbound.

Wherein, in described step 2102, forwarding statistical information is communicated with probability, link transmission ability, link average latency and link sensing satellite energy value by link obtains through composing power addition.

Wherein, in described step 21, use Link State distribution method is diffused into tethered satellite network concrete steps by link-state metric value and is:

Link-state metric value is packaged into link-state information by the 2111 current satellite nodes that carry grouping, and taking link-state information as list item link generation state table;

When other satellite node in 2112 current satellite node and the networks that carry grouping meets, they exchange link-state list separately immediately;

The 2113 current satellite nodes that carry grouping, according to the link-state list receiving, upgrade the link-state list of self.

Wherein, the link-state information in described step 2111 comprises the node identification of sequence number, the initial satellite of link, node identification and the link-state metric value that link stops satellite.

Wherein, described step 2113 concrete steps are:

If there is the inter-satellite link not occurring in self link-state list in 211301 link-state list that receive, need so, by Link State list item corresponding this link, to add in the link-state list of self;

If the Link State list item of some link in 211302 link-state list that receive, be new compared with the Link State list item of same link in self link-state list, need so to use new Link State list item to substitute the link list item of the respective links in self link-state list;

If in 211303 link-state list that receive, there is not emerging inter-satellite link, Link State list item is not new yet, so directly abandons the link-state list receiving.

The present invention compares with background technology, and the present invention mainly has the following advantages:

(1) each satellite node provides data relay service in the mode of " store-carry-forward " as other satellite node, therefore use method for routing disclosed by the invention, even at whole satellite network not full-mesh in the situation that, also there is a strong possibility, between two satellite nodes that do not have route path, realize indirect, reliable, the high efficiency of transmission of packet.

(2) in tethered satellite forwarded algorithm, take into full account that link is communicated with the energy value of probability, link transmission ability, link average latency and link sensing satellite, therefore method for routing disclosed by the invention, the satellite network communication environment the sudden change not only interim factor such as equipment fault, channel variation, malicious sabotage being caused has stronger adaptability and robustness, and possess load balancing and Energy-aware ability, can effectively extend satellite network life cycle.

Brief description of the drawings

Fig. 1 is tethered satellite network route method schematic diagram.

Embodiment

Below, in conjunction with Figure of description 1, the invention will be further described.

Tethered satellite network refers to, the satellite network of the satellite node cisco unity malfunction of preset ratio (for example exceeding 30%) or predetermined number (being for example greater than 20); Or, due to reasons such as equipment fault, channel variation, malicious sabotages, the frequent satellite network interrupting of inter-satellite link.

According to one embodiment of present invention, specific embodiments is as follows:

1. tethered satellite network route method overall plan

Each satellite node provides data relay service in the mode of " store-carry-forward " as other node, utilizes the periodically mobile communication opportunity forming of intermediate, satellite node, realizes packet in the internodal hop-by-hop transmission of source/destination.Particularly:

(1) in the time that source satellite node will send grouping to object satellite node, receive the first satellite node of this grouping, in buffer memory, store this grouping, and carry this grouping and move according to the track of self, and to set the first satellite node be the current satellite node that carries grouping.

(2) when using tethered satellite forwarded algorithm to select after down hop satellite node, the moment of meeting with down hop satellite node at the current satellite node that carries grouping, the current satellite node that carries grouping by this forwarding of packets to down hop satellite node.

(3) if down hop satellite node is object satellite node, complete transmitted in packets; Otherwise down hop satellite node, according to continuing to forward this grouping with the identical method of the first satellite node, is set as the current satellite node that carries grouping by down hop satellite node, and proceeds to step (2).

Fig. 1 has provided an embodiment of this method for routing, and (three subgraphs represent respectively t ₁, t ₂, t ₃the network topology in moment).Wherein, S is source satellite node, and D is object satellite node, and 1,2,3,4 is four intermediate, satellite nodes.Suppose that all nodes are all periodically mobile, and be ready to forward the packet that other satellite node sends, so, 1. at t ₁moment, satellite S plan sends data P to satellite D, because S and D are positioned at different connected domains, between them, there is not communication path, so satellite S for example, judges according to certain strategy (the tethered satellite network topology configuration method that hereinafter will introduce), and according to result of determination, data P is sent to the satellite 2 with its contact.Because satellite 2 does not arrive the route path of D equally, so it stores data P in internal memory, and carries P and move together, to wait for transmission opportunity.2. at t ₂in the moment, satellite 2 starts same satellite 4 and contacts, and it judges according to certain strategy equally, supposes that result of determination thinks that satellite 4 is most suitable next-hop nodes, and data P is transmitted to satellite 4 by satellite 2 so.Satellite 4 continues to move together with P.3. at t ₃in the moment, satellite 4, with D contact, is handed to D by P.

2. tethered satellite forwarded algorithm

In predetermined period, satellite node is according to initial topology structure and forward each outbound link generation state measurement value that statistical information is it, and then uses Link State distribution method that this link-state metric value is diffused into whole tethered satellite network.In the time that needs satellite node is selected down hop, this satellite node can be by the link-state metric value set receiving, splice complete satellite network topological view, then use dijkstra's algorithm to calculate down hop satellite node on this satellite network topological view.Because Dijkstra is classical graph-theoretical algorithm, repeat no more its principle.Provide an embodiment of tethered satellite forwarded algorithm below.

(1) initial topology structure

Satellite node can obtain initial topology structure from ground station, and this initial topology structure is made up of in the time period of open mode the each outbound of satellite node.

For example, ground station can be weighted and directed diagraph G=(V, E, ω by the initial topology representation of tethered satellite network _b), wherein, 1. vertex set V represents the satellite node set in network.2. collection E in limit represents the oriented link set between satellite, comprises ISL (Inter Satellite Link) satellite link and IOL (Inter Orbit Link) satellite link.3. ω _bfor representing the time varying characteristic of isl cycle opening/closing, the topological dynamics that satellite node cycle movement causes is described.For making the initial tax weights of link i → j is ω ^{i → j}(t) ∈ ω _b, can obtain ω by formula (1) ^{i → j}(t) value.In formula (1), represent that link i → j can be used for sending the time period of data, is calculated in advance by ground station.

${\mathrm{\ω}}^{i\→j}\left(t\right)=\left\{\begin{array}{cc}1,& t\∈{\mathrm{\τ}}_1^{i\→j},{\mathrm{\τ}}_2^{i\→j},{\mathrm{\τ}}_3^{i\→j},...\\ 0,& t\∈\mathrm{others}\end{array}\right.---\left(1\right)$

Ground station can be by G=(V, E, ω _b) send every satellite in tethered satellite network to, also can only send the partial information in G to each satellite.For example, for any satellite i in G, ground station only sends information ω to it ^{i → j}(t), i → j ∈ E, does the enforcement that neither affects subsequent technology scheme like this, can effectively save again the storage resources on satellite.

(2) link-state metric value

Use link-state metric value to describe the satellite network topological dynamics that the enchancement factors such as equipment fault, interim environmental change, malicious attack cause, satellite node according to predetermined period (for example, 20 seconds or 100 seconds) upgrade the forwarding statistical information of each outbound, will forward statistical information input negative exponential function and can obtain the link-state metric value of each outbound.

For example, for the note satellite link i → j ∈ link-state metric value of moment k is forwarding statistical information is have:

${\mathrm{\ω}}_E^{i\→j}\left(k\right)=e^{-c_E^{i\→j}\left(k\right)}---\left(2\right)$

1) forward statistical information

Forwarding statistical information has various definitions mode, and for example, can be communicated with the energy value that probability, link transmission ability, link average latency and link point to satellite by link and be added through composing power the forwarding statistical information that obtains satellite outbound, particularly, for note satellite link i → j ∈ E in the link capability parameter of moment k is have:

Wherein, α, β, γ and be four adjustment factors, their value can specifically arrange according to actual conditions, only need satisfy condition and .Parameter P ^{i → j}(k), Q ^{i → j}(k), E ^{i → j}and E (k) ^j(k) physical significance respectively, 1. P ^{i → j}(k) the connection probability of expression link i → j, namely, in the time period in, the history of link i → j is communicated with situation.2. Q ^{i → j}(k) represent link capability, namely, " bandwidth-Lifetime " product of link i → j.3. T ^{i → j}(k) represent that link i → j is switched to the average latency of " open mode " by " closed condition ".4. E ^j(k) represent one way link satellite pointed (for example energy value j) in link i → j.

It should be noted that and calculating P ^{i → j}(k), Q ^{i → j}(k), T ^{i → j}and E (k) ^j(k), in process, always need to use the initial topology structure that is sent to each satellite node by ground station.

(3) Link State distribution method

First, link-state metric value is packaged into link-state information by satellite node.

Secondly, each satellite node is taking link-state information as list item link generation state table.

Again, in the time that satellite node and other satellite node meet, they need to exchange link-state list separately immediately.

Finally, after exchange completes, the satellite node that participates in exchange upgrades the link-state list of self according to the link-state list receiving.

1) link-state information

Link-state information can be made up of node identification, the link-state metric value of the node identification of sequence number, the initial satellite of link, link termination satellite, as shown in formula (4).

LSI=(seq, src, dst, metric) (4) wherein, src is the mark of the initial satellite node of inter-satellite link; Dst is the mark that inter-satellite link stops satellite node; Seq is sequence number, represents the newness degree of this link-state information.Metric is the link-state metric value that initial satellite node src monitors.

2) link state update method

The mode of satellite node renewal self link-state list has multiple, provide a kind of concrete grammar below: a) one, if there is the inter-satellite link i → j not occurring in self link-state list in the link-state list receiving, need so, by Link State list item corresponding link i → j, to add in the link-state list of self.B) its two, if the Link State list item of some link in the link-state list receiving, be new compared with the Link State list item of same link in self link-state list, need so to use new Link State list item to substitute the link list item of the respective links in self link-state list.C) its three, if the link-state list relatively in this node, in the link-state list receiving, does not exist emerging inter-satellite link, Link State list item is not new yet, so directly abandons the link-state list receiving.

Claims (8)

1. a method for routing that is applicable to tethered satellite network, is characterized in that, the concrete steps of described method are:

1., when source satellite node sends grouping to object satellite node, the first satellite node that receives this grouping is stored this grouping and carries this grouping and move according to the track of self in buffer memory; Setting the first satellite node is the current satellite node that carries grouping;

2. the current satellite node that carries grouping uses tethered satellite forwarded algorithm to select down hop satellite node, and the moment of meeting with down hop satellite node at the current satellite node that carries grouping, the current satellite node that carries grouping by this forwarding of packets to down hop satellite node;

If 3. this down hop satellite node is object satellite node, complete transmitted in packets; Otherwise, this down hop satellite node is set as currently carrying the satellite node of grouping and proceeding to step 2..

2. the method for routing that is applicable to tethered satellite network as claimed in claim 1, is characterized in that, described step 2. in, use tethered satellite forwarded algorithm to select the concrete steps of down hop satellite node to be:

21 in predetermined period, each outbound link generation state measurement value that the current satellite node that carries grouping is it according to initial topology structure and forwarding statistical information, and then use Link State distribution method that this link-state metric value is diffused into whole tethered satellite network;

22 in the time that needs are selected down hop, and this current satellite node that carries grouping, by the link-state metric value set receiving, splices satellite network topological view, then uses dijkstra's algorithm on this topological view, to calculate down hop satellite node.

3. the method for routing that is applicable to tethered satellite network as claimed in claim 2, it is characterized in that, initial topology structure in described step 21 is that satellite node obtains from ground station, and this initial topology structure is made up of in the time period of open mode the each outbound of satellite node.

4. the method for routing that is applicable to tethered satellite network as claimed in claim 2, it is characterized in that, in described step 21, the concrete steps that the current satellite node that carries grouping is each outbound link generation state measurement value according to initial topology structure and forwarding statistical information in predetermined period are:

The 2101 current satellite nodes that carry grouping, by predetermined period, on the basis of initial topology structure, in conjunction with the forwarding of packets situation of self record, upgrade the forwarding statistical information of each outbound;

The 2102 current satellite nodes that carry grouping obtain forwarding statistical information input negative exponential function the link-state metric value of each outbound.

5. the method for routing that is applicable to tethered satellite network as claimed in claim 4, it is characterized in that, in described step 2102, forwarding statistical information is communicated with probability, link transmission ability, link average latency and link sensing satellite energy value by link obtains through composing power addition.

6. the method for routing that is applicable to tethered satellite network as claimed in claim 2, is characterized in that, in described step 21, use Link State distribution method is diffused into tethered satellite network concrete steps by link-state metric value and is:

Link-state metric value is packaged into link-state information by the 2111 current satellite nodes that carry grouping, and taking link-state information as list item link generation state table;

When other satellite node in 2112 current satellite node and the networks that carry grouping meets, they exchange link-state list separately immediately;

The 2113 current satellite nodes that carry grouping, according to the link-state list receiving, upgrade the link-state list of self.

7. the method for routing that is applicable to tethered satellite network as claimed in claim 6, it is characterized in that, the link-state information in described step 2111 comprises the node identification of sequence number, the initial satellite of link, node identification and the link-state metric value that link stops satellite.

8. the method for routing that is applicable to tethered satellite network as claimed in claim 6, is characterized in that, described step 2113 concrete steps are:

If there is the inter-satellite link not occurring in self link-state list in 211301 link-state list that receive, need so, by Link State list item corresponding this link, to add in the link-state list of self;

If the Link State list item of some link in 211302 link-state list that receive, be new compared with the Link State list item of same link in self link-state list, need so to use new Link State list item to substitute the link list item of the respective links in self link-state list;

If in 211303 link-state list that receive, there is not emerging inter-satellite link, Link State list item is not new yet, so directly abandons the link-state list receiving.